Month: July 2018

It is easy to calculate the carbon footprint of your home. You can calculate your carbon footprint from your heating and electricity bills. Just find the most recent ones and follow the guidance in this article. All the conversion factors are in a table at the end of this article.

For electricity, the bills usually have the full last year of energy use. The energy in electricity is measured in kilowatt-hours (kWh). Each kilowatt-hour of electricity you use that is generated by a power station costs you between 15-23c depending on where you live. Rooftop solar panels (after the subsidies and tax credits) can generate power from your roof at between 3c and 9c per kilowatt-hour, see hereso it is much cheaper to generate your own electricity than to buy it from a utility. Using one kilowatt-hour of electricity causes, on average, about 1 pound of carbon dioxide to be emitted by a power station. Generating electricity from solar panels emits zero carbon dioxide, see here. The carbon footprint of electricity varies from about 0 pounds of carbon dioxide per kilowatt-hour if the electricity is generated by hydropower to about 2 pounds per kilowatt-hour at coal-fired power stations. So just take the number of kilowatt-hours of electricity on your bill for the last year and it is roughly equal to the number of pounds of carbon dioxide emitted.

Heating oil and propane are usually reported in gallons delivered rather than gallons used but if you take what is delivered over a full year it will be pretty close to actual use. If the full year’s delivery is not written on the bill just call your delivery company and ask for the last full year’s deliveries. Burning heating oil emits about 24 pounds of carbon dioxide per gallon so just multiply the number of gallons by 24 to get the pounds of carbon dioxide emitted from heating oil. Propane emit about 13 pounds per gallon so just multiply the gallons delivered in a full year by 13.

Burning natural gas emits about 12 pounds of carbon dioxide per Therm or 120 pounds per million BTUs. BTU is short for British Thermal Unit. A Therm is 100,000 BTUs. Like kilowatt-hours, both are units of energy. So just multiply the number of Therms used by 12 to get the pounds of carbon dioxide emitted from burning natural gas. If your bill is in millions of BTUs (sometimes written MMBTU) then multiply the number of million BTUs used by 120.

You can greatly reduce the carbon footprint caused by heating your house by installing heat pumps to replace, or supplement, your furnace. See here. If you have heat pumps powered by your own solar panels then you can heat your house with a zero-carbon footprint. See here. Heating your house with heat pumps powered by electricity is from solar panels is now the cheapest way to heat your house, even cheaper than heating it with natural gas.

Then just add up the total pounds of carbon dioxide emitted by your house from heating and from electricity. This gives you the total primary carbon footprint of your house in pounds of carbon dioxide. If you prefer to see it in tons, just divide the number of pounds by 2,000. If you came out to somewhere between 5 tons and 50 tons you probably did the calculations correctly.

For example:

If you had 1,000 gallons of heating oil delivered in the last year, which is fairly typical in Massachusetts, then you emitted 1,000 gallons x 24lbs CO2/gallon = 24,000lbs of carbon dioxide from burning heating oil. If you used 1,000 Therms (100 million BTUs) of natural gas, which is also fairly typical in Massachusetts, then you emitted 1,000 Therms x 12lbs CO2/Therm = 12,000lbs of carbon dioxide from burning natural gas. If, in addition, you used 7,000 kilowatt-hours of electricity, again about average in Massachusetts, then you caused about 7,000lbs of carbon dioxide emissions from power stations burning fuels to make the electricity you used. So in the heating oil example your total emission of carbon dioxide was 7,000lbs + 24,000lbs = 31,000lbs (15.5 tons). In the natural gas example it was 7,000lbs + 12,000lbs = 19,000lbs (9.5 tons).

If you found this post helpful you will almost certainly find the book, Zero Carbon Home, even more helpful. It is written in the same easy-to-read style backed by the same rigorous scientific approach and financial analysis. The book costs $20 and is available by clicking here.